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From: wls@astrovax.UUCP (William L. Sebok)
Newsgroups: net.unix
Subject: Re: Asynchronous I/O on UNIX?
Message-ID: <692@astrovax.UUCP>
Date: Mon, 2-Dec-85 16:21:34 EST
Article-I.D.: astrovax.692
Posted: Mon Dec  2 16:21:34 1985
Date-Received: Tue, 3-Dec-85 20:15:09 EST
References: <248@well.UUCP> <241@ll-xn.ARPA> <604@unisoft.UUCP>
Reply-To: wls@astrovax.UUCP (William L. Sebok)
Organization: Princeton Univ. Astrophysics
Lines: 17

In article <604@unisoft.UUCP> paul@unisoft.UUCP (n) writes:
>	The major problem in implementation under Unix is the concept of IO
>context, with Unix an IO's context (u_base, u_count, u_offset) are in a
>processes 'udot' if you are going to be doing multiple IO's you need to be
>able to send this information to the device with the queued IO (you also have
>to send the process ID, the completion routine's virtual address and the
>parameter you are going to give to the completion routine).

I noticed that in the transition from the 4.1 BSD to the 4.2 BSD kernel,
references in the i/o drivers to u.u_base, u.u_count, u.u_offset are replaced
by references to members of a uio structure.  This was the only change (that I
remember) that I had to make in some locally written drivers I ported.  I
wondered and still wonder if this change means that support of asynchronous
i/o is in the works in BSD.
-- 
Bill Sebok			Princeton University, Astrophysics
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